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author | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-10-24 18:45:36 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-10-25 04:05:27 +0300 |
commit | a970174d7a1010cb29a5b0c9fa0626abdefcfcbe (patch) | |
tree | dd0efb49091012750a00a3ccf32f71dadb7e252d /arch | |
parent | 337a0a0b63f1c30195733eaacf39e4310a592a68 (diff) | |
download | linux-a970174d7a1010cb29a5b0c9fa0626abdefcfcbe.tar.xz |
x86/mm: Do not verify W^X at boot up
Adding on the kernel command line "ftrace=function" triggered:
CPA detected W^X violation: 8000000000000063 -> 0000000000000063 range: 0xffffffffc0013000 - 0xffffffffc0013fff PFN 10031b
WARNING: CPU: 0 PID: 0 at arch/x86/mm/pat/set_memory.c:609
verify_rwx+0x61/0x6d
Call Trace:
__change_page_attr_set_clr+0x146/0x8a6
change_page_attr_set_clr+0x135/0x268
change_page_attr_clear.constprop.0+0x16/0x1c
set_memory_x+0x2c/0x32
arch_ftrace_update_trampoline+0x218/0x2db
ftrace_update_trampoline+0x16/0xa1
__register_ftrace_function+0x93/0xb2
ftrace_startup+0x21/0xf0
register_ftrace_function_nolock+0x26/0x40
register_ftrace_function+0x4e/0x143
function_trace_init+0x7d/0xc3
tracer_init+0x23/0x2c
tracing_set_tracer+0x1d5/0x206
register_tracer+0x1c0/0x1e4
init_function_trace+0x90/0x96
early_trace_init+0x25c/0x352
start_kernel+0x424/0x6e4
x86_64_start_reservations+0x24/0x2a
x86_64_start_kernel+0x8c/0x95
secondary_startup_64_no_verify+0xe0/0xeb
This is because at boot up, kernel text is writable, and there's no
reason to do tricks to updated it. But the verifier does not
distinguish updates at boot up and at run time, and causes a warning at
time of boot.
Add a check for system_state == SYSTEM_BOOTING and allow it if that is
the case.
[ These SYSTEM_BOOTING special cases are all pretty horrid, but the x86
text_poke() code does some odd things at bootup, forcing this for now
- Linus ]
Link: https://lore.kernel.org/r/20221024112730.180916b3@gandalf.local.home
Fixes: 652c5bf380ad0 ("x86/mm: Refuse W^X violations")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/x86/mm/pat/set_memory.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 97342c42dda8..2e5a045731de 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -587,6 +587,10 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star { unsigned long end; + /* Kernel text is rw at boot up */ + if (system_state == SYSTEM_BOOTING) + return new; + /* * 32-bit has some unfixable W+X issues, like EFI code * and writeable data being in the same page. Disable |